A fuel injector must perform its prime function of delivering a desired fuel charge to an engine cylinder within a number of constraints. The first such constraint is a physical space constraint. The fuel injector must reside coincident with a plurality of valves and valve springs. With the need for increased efficiencies of internal combustion engines, the number of valves that service a cylinder has grown from the traditional two valves common only a few years ago to three, four, and even five valves. The fuel injection unit is forced to reside within the cluster of valves servicing the cylinder.
Another constraint within which the fuel injector must live is the need to provide adequate fluid sealing for a number of different passageways that must be coupled to the fuel injector. Due to manufacturing tolerances and the great fluid pressures involved, it has in the past proved difficult to consistently and effectively simultaneously seal the various fluid passageways that are coupled to the fuel injector. Additionally, present means for clamping the fuel injector to the engine cylinder head have imposed torque moments to the passageway seals, the torque moments contributing to seal leakage over time.
A fluid passageway that must be sealed is the passageway surrounding the injector tip where the tip projects into the combustion chamber. The pressure generated by ignition of the injected fuel is typically on the order of 2,500 pounds per square inch acting to leak around the fuel injector tip.
A number of current fuel injector designs employ a high pressure engine lubricating oil to actuate an intensifier plunger within the fuel injector to bring the pressure of the fuel at the time of injection up to approximately 20,000 pounds per square inch. The high pressure lubricating oil is delivered through a rail defined in the cylinder head to the fuel injector. The high pressure lubricating oil is typically at a pressure of approximately 3,500 pounds per square inch. The high pressure lubricating oil must be fluidly coupled from the rail to the fuel injector. This is a second fluid passageway that must be sealed.
There is a need in the industry to consistently clamp the fuel injector into place on the cylinder head. The clamping action must effect fluid seals at least at the injector tip and at the interface with the high pressure lubricating oil rail. Additionally, the means for clamping must be compatible with the limited space available in the cluster of valves servicing at the cylinder. Further, it would be a benefit to the industry for the clamping to minimize the effects of manufacturing tolerances on effecting the fluid seals and minimizing the torquing forces that the clamping action subjects the various fluid seals to.